Taste buds, the sensory end organs that transduce gustatory stimuli into neural signals, reside in taste papillae in the mammalian tongue. Therefore, taste papillae incorporate the epithelium that will differentiate to include cells of taste bud. However, the field of taste biology lacks a clear understanding of what constitutes possible taste cell precursors in developing papillae. In fact, there is no detailed information about cell specification of the early lingual epithelium that can cross-signal to underlying mesenchyme in papilla differentiation. The goals of this proposal are to characterize: (1) the localization and timing for neuronal, glial and taste cell phenotypes in embryonic and early postnatal tongue epithelium;(2) stage and location-specific distribution and phenotypic specification of neural crest derived cells (NCDCs) in developing lingual epithelium, mesenchyme and taste papillae. Immunohistochemistry on whole tongue and sections will be used to characterize and localize neuronal, glial and taste cell phenotypes, in embryonic and postnatal tongue epithelium and mesenchyme. Also, an in vitro, tongue organ culture system at select embryonic stages will be used to study whether cell types can develop and be sustained in the absence of an intact sensory contribution. We will use transgenic mouse lines with a lacZ (R26R) reporter or ZEG (lacZ/EGFP) double reporter transgene modulated by Wnt1- Cre or P0-Cre to label Wnt1- and P0-expressing NCDCs. The distribution and cell phenotypes of NCDCs in the developing tongue and taste papillae will be characterized. The results will bring new information to the field and provide an important foundation for understanding the derivation and progressive differentiation of developing taste papilla epithelium. Taste sensation, which is tranduced by taste buds in the gustatory papillae, guides nutritive choices and ingestive behaviors of all vertebrates. Thus a thorough knowledge of how taste papillae develop and differentiate to eventually include taste bud cells will contribute to better understanding how taste sensation develops. Public Health Relevance: The sense of taste informs our nutritive choices, which are essential for life and quality of life. Knowledge of taste papilla development will contribute to understanding how the distribution and density of tongue taste organs are determined, and therefore, to understanding how taste sensitivity emerges.